1. Field of the Invention
The present invention relates to a golf ball. More specifically, the present invention relates to a solid three-piece golf ball with an aerodynamic surface geometry, a relatively thin cover, a high core compression, a high cover hardness and an initial velocity limited to less than 255 feet per second.
2. Description of the Related Art
The traditional golf ball, as readily accepted by the consuming public, is spherical with a plurality of dimples, with each dimple having a circular cross-section. Many golf balls have been disclosed that break with this tradition, however, for the most part these non-traditional golf balls have been commercially unsuccessful.
Most of these non-traditional golf balls still attempt to adhere to the Rules Of Golf, as set forth by the United States Golf Association (“USGA”) and The Royal and Ancient Golf Club of Saint Andrews (“R&A”), which have placed controls on the construction and performance of golf balls. As set forth in Appendix III of the Rules of Golf, the weight of the ball shall not be greater than 1.620 ounces avoirdupois (45.93 g), and the diameter of the ball shall not be less than 1.680 inches (42.67 mm), which is satisfied if, under its own weight, a ball falls through a 1.680 inches diameter ring gauge in fewer than 25 out of 100 randomly selected positions, the test being carried out at a temperature of 23±1° C. In addition, the ball must not be designed, manufactured or intentionally modified to have properties, which differ from those of a spherically symmetrical ball.
One example is Shimosaka et al., U.S. Pat. No. 5,916,044, for a Golf Ball that discloses the use of protrusions to meet the 1.68 inches (42.67 mm) diameter limitation of the USGA and R&A. The Shimosaka patent discloses a golf ball with a plurality of dimples on the surface and a few rows of protrusions that have a height of 0.001 to 1.0 mm from the surface. Thus, the diameter of the land area is less than 42.67 mm.
Another example of a non-traditional golf ball is Puckett et al., U.S. Pat. No. 4,836,552 for a Short Distance Golf Ball, which discloses a golf ball having brambles instead of dimples in order to reduce the flight distance to half of that of a traditional golf ball in order to play on short distance courses.
Another example of a non-traditional golf ball is Pocklington, U.S. Pat. No. 5,536,013 for a Golf Ball, which discloses a golf ball having raised portions within each dimple, and also discloses dimples of varying geometric shapes, such as squares, diamonds and pentagons. The raised portions in each of the dimples of Pocklington assist in controlling the overall volume of the dimples.
Another example is Kobayashi, U.S. Pat. No. 4,787,638 for a Golf Ball, which discloses a golf ball having dimples with indentations within each of the dimples. The indentations in the dimples of Kobayashi are to reduce the air pressure drag at low speeds in order to increase the distance.
Yet another example is Treadwell, U.S. Pat. No. 4,266,773 for a Golf Ball, which discloses a golf ball having rough bands and smooth bands on its surface in order to trip the boundary layer of air flow during flight of the golf ball.
Aoyama, U.S. Pat. No. 4,830,378 for a Golf Ball with Uniform Land Configuration, discloses a golf ball with dimples that have triangular shapes. The total flat land area of Aoyama is no greater than 20% of the surface of the golf ball, and the objective of the patent is to optimize the uniform land configuration and not the dimples.
Another variation in the shape of the dimples is set forth in Steifel, U.S. Pat. No. 5,890,975 for a Golf Ball and Method of Forming Dimples Thereon. Some of the dimples of Steifel are elongated to have an elliptical cross-section instead of a circular cross-section. The elongated dimples make it possible to increase the surface coverage area. A design patent to Steifel, U.S. Pat. No. D406,623 has all elongated dimples.
A variation on this theme is set forth in Moriyama et al., U.S. Pat. No. 5,722,903 for a Golf Ball, which discloses a golf ball with traditional dimples and oval shaped dimples.
A further example of a non-traditional golf ball is set forth in Shaw et al., U.S. Pat. No. 4,722,529 for Golf Balls, which discloses a golf ball with dimples and 30 bald patches in the shape of a dumbbell for improvements in aerodynamics.
Another example of a non-traditional golf ball is Cadorniga, U.S. Pat. No. 5,470,076 for a Golf Ball, which discloses each of a plurality of dimples having an additional recess. It is believed that the major and minor recess dimples of Cadorniga create a smaller wake of air during flight of a golf ball.
Oka et al., U.S. Pat. No. 5,143,377 for a Golf Ball, discloses circular and non-circular dimples are square, regular octagonal, regular hexagonal and amount to at least forty percent of the 332 dimples on the golf ball of Oka. These non-circular dimples of Oka have a double slope that sweeps air away from the periphery in order to make the air turbulent.
Machin, U.S. Pat. No. 5,377,989 for Golf Balls with Isodiametrical Dimples, discloses a golf ball having dimples with an odd number of curved sides and arcuate apices to reduce the drag on the golf ball during flight.
Lavallee et al., U.S. Pat. No. 5,356,150, discloses a golf ball having overlapping elongated dimples to obtain maximum dimple coverage on the surface of the golf ball.
Oka et al., U.S. Pat. No. 5,338,039, discloses a golf ball having at least forty percent of its dimples with a polygonal shape. The shapes of the Oka golf ball are pentagonal, hexagonal and octagonal.
The golf ball rules further require that a golf ball have an overall distance no greater than 296.8 yds (the limit is 280 yds, or 256 m, plus a six percent tolerance for the total distance of 296.8 yds) and an initial velocity no greater than 255.0 ft/s (the limit is 250 ft/s or 76.2 m/s, with a two percent maximum tolerance that allows for an initial velocity of 255 ft/s) measured on a USGA approved apparatus.
The initial velocity test for conformance is comprised of a large 275 pound wheel that rotates around a central axis at a rate of 143.8 feet per second (striker tangential velocity) and strikes a stationary golf ball resting on a tee. The wheel has a flat plate that protrudes during its final revolution prior to impact with the golf ball. The ball's velocity is then measured via light gates as it travels approximately six feet through an enclosed tunnel. Balls are kept in an incubator at a constant temperature of 23 degrees Celsius for at least three hours before they are tested for initial velocity performance. To test for initial velocity, balls are placed on a tee and hit with the metal striker described above. Twenty-four balls of a particular type make up one test. Each ball is hit with the spinning wheel a total of four times. The highest and lowest recorded velocities are eliminated and the remaining two velocities are averaged to determine the ball speed for that specific ball. The individual speeds of the 24 balls in the group are then averaged, and that is considered the mean initial velocity (IV) of the group for the test.
For USGA conformance purposes, a ball with a mean initial velocity of less than 255.0 ft/s is considered conforming to the USGA Rule of Golf and can be played in sanctioned events. For reference to the USGA Wheel Test see the USGA web-site at www.usga.com, or reference U.S. Pat. No. 5,682,230 for further information.
Generally speaking, the USGA IV test is designed to be a consistent measurement tool capable of regulating the speed (and ultimately distance) of golf balls. It is commonly known in the industry that golf ball manufacturers perform a simpler test on prototype golf balls and then attempt to correlate the results to the USGA Wheel Test. One type of correlation test is the Coefficient of Restitution (“COR”) test, which consists of firing a golf ball from a cannon into a fixed plate and taking the ratio of outgoing velocity to incoming velocity.
The Coefficient of Restitution is the ratio of the velocity of separation (Vout1−Vout2) to the velocity of approach (Vin1−Vin2), where COR=(Vout1−Vout2)/(Vin1−Vin2). The value of COR will depend on the shape and material properties of the colliding bodies. In elastic impact, the COR is unity and there is no energy loss. A COR of zero indicates perfectly inelastic or plastic impact, where there is no separation of the bodies after collision and the energy loss is a maximum. In oblique impact, the COR applies only to those components of velocity along the line of impact or normal to the plane of impact. The coefficient of restitution between two materials can be measured by making one body many times larger than the other so that m2 (mass of larger body) is infinitely large in comparison to m1 (mass of the smaller body). The velocity of m2 is unchanged for all practical purposes during impact andCOR=Vout/Vin
One particular type of COR test device that is commonly used in the golf ball industry is the ADC COR machine developed by Automated Design Corporation. Based on the definition of COR above, m2 is a large 400 lb plate fixed vertically that the ball (m1) is fired into. The impact of the golf ball to the large fixed plate is an oblique impact. Software developed by Automated Design Corporation accurately calculates the normal velocities given the dimensions of the machine and outputs a value for Coefficient of Restitution as defined above.
U.S. Pat. No. 5,209,485, filed in 1991, discloses a restricted flight golf ball that has a reduced COR. However, the '485 patent also discloses, for comparison purposes, that the TOP FLITE®XL golf balls, manufactured and sold by Spalding had a COR value of 0.813 when fired at a speed of 125 ft/s. The '485 patent also discloses that the Spalding SUPER RANGE golf ball had a COR value of 0.817 when fired at a speed of 125 ft/s. However, the SUPER RANGE golf ball was a non-conforming golf ball and thus had an IV value greater than 255 ft/s.
U.S. Pat. No. 5,803,831, filed in 1996 discloses in Table 14 a finished solid three-piece golf ball that has a COR of 0.784 at a speed of what is believed to be 125 ft/s.
Although the prior art has set forth numerous variations for the surface of a golf ball, the prior art golf balls fail to provide an aerodynamic golf ball with a surface that minimizes the volume needed to trip the boundary layer of air at low speeds while providing a low drag level at high speeds and that conforms to the USGA IV limit of 255 feet per second while having a high COR.